Increasing evidence suggests important events in T cell maturation in the thymus and tolerance induction are governed by specific gene regulation. Recent studies also suggest T cell tolerance comes about through mechanisms other than clonal deletion. We have been studying a model of clonal T cell inactivation where stimulation of the T cell receptor can lead to a functional inactivation or anergy of the cell. This is manifested by an inability to produce IL-2. Our preliminary studies have shown that anergy is due to abnormalities in nuclear regulatory proteins that lead to faulty IL-2 gene induction. In the thymus, precursor cells undergo a complex set of developmental events and emerge as T lymphocytes capable of specific antigen recognition. The central molecular controlling events for this process are totally obscure. We are taking several approaches to this problem. First, we have initiated studies of various CD3 chain genes which have different developmental activation profiles. Understanding the nuclear regulatory proteins for these genes may lead to the discovery of primary developmental regulatory proteins. Second, we are generating subtractive cDNA libraries from different stage thymocytes to clone genes for developmental regulatory factors. Third, we will study the role and regulation of IL-2 in the maturation of thymocytes that do not bear antigen receptor. In conjunction with these lines of investigation we will also use thymic regeneration after sublethal irradiation as a clinically relevant model for T cell maturation under conditions in which the thymus has been pathologically perturbed.